To investigate what factors affect the rate of Photosynthesis.

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20 October, 2002           Coursework/Sc1           Amandeep Virk

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PLANNING

  • Task: To investigate what factors affect the rate of Photosynthesis.

INTRODUCTION

        All green plants use raw materials from their surrounding atmosphere to make their own food. They do this by a process called Photosynthesis. Green plants contain many tiny structures called Chloroplasts and these contain a chemical called Chlorophyll. This chemical is a very important part of Photosynthesis, as this is where the plant, to produce its own food, absorbs sunlight. Photosynthesis mainly takes place in the Palisade Mesophyll cells, which are situated near the top of the leaf. These cells contain lots of Chloroplasts, which are closely packed together, so that they can trap the most amount of sunlight possible.

Diagram To Show How Photosynthesis Takes Place In a Leaf

(This diagram is taken from ‘Biology for you’ by Gareth Williams)

        The main purpose of Photosynthesis is for a plant to produce oxygen and glucose so that the plant can grow. It does this by absorbing light energy in chlorophyll and using this energy to change the two main raw materials, (Carbon Dioxide, and Water) into glucose and oxygen. The oxygen is the waste product from photosynthesis and therefore goes into the atmosphere. The glucose goes onto to be stored by the plant. The plant can not store the glucose, as it is, it has to be turned into starch. The starch is then used as food and is stored for when it is needed. Photosynthesis is a complex reaction and can be summed up in an equation:

carbon dioxide   +      water         light and chlorophyll     glucose   +  oxygen

         6 CO                    6 H O                                                  C  H  O          6 O

FACTORS THAT EFFECT PHOTOSYNTHESIS                   Amandeep Virk

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  • Light: This factor is just as important as the others are in Photosynthesis, without it photosynthesis would simply not take place. It has an effect on the rate of photosynthesis and depending on the availability and source of light, it can make photosynthesis occur either faster or slower. The amount of light can only increase to a point because chlorophyll can only absorb a certain amount of light. Therefore light is a limiting factor because the rate of photosynthesis can increase if the intensity of light is strong, but only to a point, after that the rate of photosynthesis stays constant. Sometimes the rate of photosynthesis can reduce because too much light can bleach chlorophyll and make the leaf less efficient. 
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  • Temperature: Photosynthesis can occur without this factor but it would be a very slow process. As temperature increases the rate of photosynthesis does too. Again, temperature is a limiting factor because if it increases over 40°C, the enzymes are destroyed because it is too hot. The enzymes can also be destroyed if the temperature is too low. Cold conditions can make the enzymes not work properly.

  • Carbon Dioxide: Plants cannot photosynthesize without carbon dioxide present. The concentration of carbon dioxide is not a limiting factor because the most carbon dioxide there is available to plants; the ...

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